This invention relates to an oxygen supply unit for installation in an overhead panel above a row of seats in the passenger cabin of an aircraft.
A known oxygen supply unit includes a number (typically four) of face masks which are normally housed, in a stowed condition, inside a casing located in the overhead panel.
Each mask is connected to a source of oxygen by a respective supply line, comprising a flexible hose and a so-called check valve which is used to exercise control over the flow of oxygen to the mask. When the unit is inoperative (i.e. when a supply of oxygen is not required) a removable pin, received in a hole in the body of the check valve, retains a valve member thereof in the closed condition, thereby preventing oxygen from being supplied to the mask. In the event of an emergency, occasioned, for example, by a pressure drop in the passenger cabin, a pivotal cover of the casing is caused to open. This enables the masks within the casing to drop down to assume a deployed position whereby to be accessible to passengers occupying the seats below the unit. Each removable pin is tethered to a respective flexible hose by means of a lanyard or cord so that when a face mask is grasped by a passenger and pulled down to his face, the pin, tethered to the associated hose, is withdrawn from the check valve allowing oxygen to flow to the mask.
Existing oxygen supply units have the disadvantage that the pin associated with one mask could be fitted inadvertently to the check valve connected to a different mask. In these circumstances, when the pin is withdrawn from the (incorrect) check valve, oxygen would not be supplied to the intended mask. Clearly, this could have dire consequences.